There have been a couple of handfuls of experimental Rolls-Royce models built over the past 100 years, but up to now they’ve all had a conventional petrol engine mounted behind the Spirit of Ecstasy. So when the company unveiled a battery-electric Phantom model at this year’s Geneva motor show, we did a double take.

Granted, Henry Royce, like Ferdinand Porsche, first trained as an electrical engineer, but surely not even the world’s reserves of Duracells would be enough to power a 2.5-ton super limousine.

Besides, what was the point? Rolls-Royce’s existing BMW-sourced 6.75-litre 453bhp/531lb ft V12 already provides the sort of down-and-dirty torque that wafts the Phantom about as if powered by the sun. And wasn’t it the 1955 Rolls-Royce Silver Cloud advertising line that ran: “At 60mph the loudest noise in this new Rolls-Royce comes from the electric clock”?

In other words, all of the advantages of electric traction were already present with the exception of any CO2 savings. In well-to-wheel terms the EE produces 193g/km compared to the standard car’s tailpipe emissions of 377g/km.

It was with a slightly sceptical heart that I drove down to R-R’s Goodwood factory in Sussex to sample the battery car.

As well as trying out the delights of battery-electric drive, the company has taken the opportunity to experiment with a new form of ceramic-flecked paintwork and the pale-turquoise car that stood outside reception looked as art deco as an exhibit in the 1939 New York World’s Fair.

It might not be to everyone’s taste, but the iridescent coachwork certainly makes a statement. So, too, does the eerily-blue illuminated plastic (Makrolon) Spirit of Ecstasy on the Grecian radiator, which looks like one of those priceless Lalique mascots of the between wars period.

In the cabin there’s a new vegetable-dyed leather, which is warm to the eye and soft to the touch, although only time will tell if this finish remains unfaded and as tactile.

Since the Phantom EE is embarking on a year-long world tour where it will be driven by all comers and stand out in all weathers, perhaps this is a perfect test bed.

Under the bonnet are five separate battery packs to maximise the space usage. These Axion Power packs contain 96 Dow Kokam Lithium-Nickel-Cobalt-Manganese-Oxide cells, which weigh 1,410lb and pack a 71kWh punch (by contrast the forthcoming Vauxhall Ampera has a 400lb, 16kWh battery pack).

Rolls-Royce says the cost of a battery-electric Phantom like this would be well over twice the current £285,200 list price of a standard model – we estimate the cost of the battery pack alone is significantly more than £100,000.

Engineered by Lotus Engineering, the Phantom EE uses two 145kW (194bhp) AC motors from the Tesla sports car, which are cleverly fitted above the rear differential, which is turned through 90 degrees so the drive feeds vertically downwards.

Without the petrol engine and six-speed automatic transmission, but with the battery, motors and sound proofing, the Phantom EE’s kerb weight is 440lb over that of the standard Phantom.

Inside there are some subtle changes to indicate the volt-based driveline. The instrument backing matches the coachwork, there’s a battery-charge indicator instead of a fuel gauge and the power reserve indicator is remapped to show overrun recharging. The centre console hatch reveals a recharging meter.

Ah, recharging. This really is the car’s Achilles’ heel – it takes 20 hours on a domestic UK supply, although Rolls has fitted a three-phase system and an experimental induction wireless charging system, both of which are capable of a full recharge in less than eight hours.

Push the starter to ready the systems and then pull the steering wheel gearlever quadrant through to drive and you’re ready for the off.

There’s no creep built into the system, which is a mistake as on any incline the Phantom will roll back. Get on the throttle and the car wafts away with maximum torque at near zero revs; the sensation is similar to that of the V12 standard car.

What’s lacking is the unburstable sensation of the petrol engine and the electronic rack and pinion steering also lacks the finesse of the standard system. Nor is the electric Phantom entirely quiet, either, in spite of the considerable sound insulation packed between the twin floors. There’s a slight whirring if you accelerate hard and the tyres make their presence felt as well.

A similar run in the standard petrol Phantom proves that, if anything, at low speeds, it is the quieter and more refined car, although the electric Phantom is by far the most refined battery electric car we’ve yet driven.

Once up to speed, you can feather the throttle and allow the Rolls to coast along. Selecting the Low button on the steering wheel increases the recharging and driveline drag, although it’s a bit too much unless you are descending a steep hill.

And boy does that battery capacity disappear quickly. We started with a quarter charge and headed for home after a brief foray up the Sussex Alps with range anxiety written over our faces.

As an exercise into the possible, the EE is quite brilliant. As a practical proposition, it’s a disaster, partly because of the paltry range, but mainly because of the insanely long recharge times.

Rolls-Royce is well aware of the drawbacks and other environmental alternatives are being looked at. BMW has an active hydrogen research programme using the V12 engine, but the battery-electric car could be made a great deal more practical with the addition of a range-extender motor.

“We’re not ruling anything out,” said a spokesman. With arch-rival Bentley looking at diesel and hybrid power, Rolls-Royce will need to make some decisions on its future direction soon. Watch this space.

Verdict: A fine piece of engineering, which proves the advantages as well as the considerable drawbacks of battery-electric power

Telegraph verdict: Three out of five stars

RIVALS

Nissan Leaf, £25,990

Battery-electric power in a rather more prosaic form. The 2011 Car of the Year goes on sale this year priced at £25,990 including a £5,000 Government grant. This front-wheel-drive, family hatchback seats four with a top speed of 90mph, 0-62mph acceleration in 12sec and a range of 100 miles as long as you drive it like there's a raw egg on the bonnet.

Fisker Karma, £81,500

We're still waiting for this plug-in hybrid four-door coupé from the former BMW and Aston Martin design boss, but the signs are promising on paper. With a top speed of 125mph, 0-60mph in 5.1sec, an electric range of 50 miles and 37.7mpg when the four cylinder engine starts, the Karma shows potential, although the price of £81,500 might put a few people off.